Phase Detecting Pixels (PDPs) on a back side illuminated (BSI) complementary metal oxide semiconductor (CMOS) image sensor are useful for improving focus in a camera. Pairs of pixels are masked such that they detect light only from one or other edge of an objective lens. A pair of complimentary PDPs is positioned on the sensor to allow the camera to determine how out-of-phase received light is at that position, and thereby determine lens focusing adjustments needed to focus the image on the sensor.
Conventional manufacturing of a BSI CMOS image sensor with PDPs forms PDP masks for each PDP when forming a metal grid of a composite grid (oxide over metal) layer that also includes a buried color filter array (BCFA). Thus, the PDP masks are also positioned within the composite grid.
A BSI CMOS image sensor manufactured using a composite grid may obtain a higher quantum efficiency (QE), as compared with a BSI CMOS image sensor manufactured with a BCFA; however, phase detection ability is degraded because of the additional oxide above the PDP mask.